This invention relates to a gear train of an electronic timepiece in which the timepiece analogue display is driven every 1 second, are relates further to a gear train in a small-sized electronic timepiece having analogue display wherein the layout of said timepiece is such that a timepiece battery does not protrude out of the periphery of a timepiece plate.
In the conventional analogue electronic timepiece of this type, the gear train has been arranged as follows, a second wheel is put in the center of the timepiece and a battery is positioned at the side of said second wheel to get maximum space for battery. Said second wheel has a gear, whose number of teeth is 60. A jumper engaging the second wheel resiliently indexes said wheel. Under the present state of precision fabrication, it is very difficult to machine accurately a gear wheel, the profile of which has the shape of the main gear train for a timepiece and which has the outer diameter not greater than 3.7 millimeters and 60 teeth and a module not greater than 0.06 millimeters. Therefore the available diameter of the gear wheel is somewhat large, so the space to receive the battery is positioned distant from the center of the timepiece. The outer diameter of a regular battery for a man's watch is about 11.6 millimeter. When the regular battery is arranged adjacent to the second wheel, the radius of the plate which surrounds the battery completely comes to not less than 13.45 millimeters. This value does not contain the clearance between the battery and the second wheel or other member. When said clearance is considered, the radius of the plate or movement comes to more than 14 millimeters. Assuming that the outer diameter of the plate is 26 millimeters, the arranged battery will protrude about 1 millimeter outof the plate. Namely the maximum radius of the movement is given by the sum of the radius of the second wheel, the diameter of the battery and said clearance. Therefore if it is wanted to design the plate rather small, the battery will protrude out of the plate. In this case the watch case needs a recess receiving said battery so the cost of manufacturing is high. And if it is wanted to arrange the battery within the plate, the diameter of the plate must be large enough to include said maximum radius which is given by the radius of the second wheel, the diameter of the battery and the clearance between the battery and the second wheel or other member. In this case the size of the watch is large so a case having a good appearance has not been available.